Plate fins



April 1969 A. Y. GUNTER 3,438,433

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Filed May 9, 1967 h-MB Ac/au on K Gun/"er INVENTOR United States Patent 3,438,433 PLATE FINS Addison Y. Gunter, Houston, Tex., assignor to Hudson Engineering Corporation, Houston, Tex. Filed May 9, 1967, Ser. No. 637,188 Int. Cl. F28d 1/04 US. Cl. 165-151 10 Claims ABSTRACT OF THE DISCLOSURE A plate fin having laterally and longitudinally extending rows of holes with their axes arranged perpendicularly to one another and at least one louver in the area of the plate intermediate the axes of adjacent laterally and longitudinally extending rows of holes which extends longitudinally parallel to and asymmetrically of a straight line parallel to and equidistant the axes of adjacent longitudinally extending rows.

This invention relates to plate fins for use in tube bundles adapted to be installed in air coolers or the like. More particularly, it relates to improvements in plate fins of the type in which the holes for receiving the tubes are adapted to dispose the tubes in line with the air flow therepast and in which surface areas of the plate intermediate the holes are interrupted by means of louvers or the like.

As well known in this art, in the construction of a tube bundle, a multiplicity of closely spaced apart plate fins are tightly engaged about an assembly of laterally and longitudinally extending rows of side-by-side tubes to form a module or brick. Thus, each plate has holes in its corresponding in spacing and number to the tubes so as to form a fin common to all the tubes. Headers are then connected to the ends of the tubes of the module to form a bundle. As contemplated by this invention, the axes of the longitudinally and laterally extending rows of holes are perpendicular to one another, so that the resulting pattern of the tubes is rectangular, whereby, as above-mentioned, the tubes of the bundle may be disposed in line with air flow past them.

As well known in the art, interruptions such as louvers may be so arranged on the fin surface intermediate the holes as to improve their heat transfer characteristics. In the design of plate fins having such interruptions, it is necessary to take into account not only the heat exchange characteristics, but also the resulting static pressure loss.

In some cases, the heat transfer rate of the tube side fluid is so low that it is the controlling consideration, since the increase in air flow necessary to increase the heat transfer would not justify the resulting static pressure loss. On the other hand, in other cases, the heat transfer rate of the tube side fluid may be sufficiently large to justify the increased static pressure loss. In the past, these conflicting considerations have required the selection of one or the other of two plate fin designs.

An object of this invention is to provide a plate fin which is suitable for use in a tube bundle regardless of which consideration is controlling.

A more particular object is to provide such a plate fin which permits the module to be arranged in such a way as to selectively increase or decrease the heat exchange rate and the static pressure loss without changing the air flow.

A still further object is to provide such a plate fin which is of simple and inexpensive construction.

These and other objects are accomplished, in accordance with the present invention, by a plate fin having each of its areas intermediate the axes of adjacent laterally and longitudinally extending rows of holes interrupted in such a manner that the heat transfer rate and static pressure loss in the resulting tube bundle are increased or decreased depending on the direction of air flow therepast. More particularly, the plate has at least one longitudinally extending interruption arranged in each such area asymmetrically of a straight line extending parallel to and equidistant the axes of adjacent longitudinally extending rows.

In this way, each such interruption is closer to the throat between adjacent holes of one longitudinally extending row of holes than to the throat between adjacent holes of an adjacent longitudinally extending row. Consequently, the module may be so arranged that the plate fins are disposed with each such interruption nearer a throat downstream of air flow past a longitudinal edge of plate. Alternatively, and upon reversal of the module the plates are disposed with each such interruption nearer a throat upstream of air flow past its other longitudinal edge. As will be explained more fully hereinafter, in the second instance, there will be greater heat transfer and static pressure loss; and, in the first instance, there will be less heat transfer and static pressure loss. Thus, the module may be used as desired depending on which of the above-mentioned considerations controls.

In the drawings, wherein like reference characters are used throughout to designate like parts:

FIG. 1 is a perspective view of a typical tube bundle in which the plate fins of the present invention may be used;

FIG. 2 is a plan view of one end of one embodiment of such a plate fin so arranged with respect to air flow therepast as to provide a high heat transfer and static pressure loss;

FIG. 3 is a view similar to FIG. 2, but with the plate fin turned 180 so as to arrange it with respect to air flow in such a manner as to provide low heat transfer and static pressure loss;

FIG. 4 is a perspective view on an enlarged scale of a corner of the plate fin of FIGS. 2 and 3;

FIG. 5 is a plan view of one end of another embodiment of such a plate fin which, similarly to the plate fin of 'FIG. 2, is so arranged with respect to air flow therepast as to provide a high heat transfer rate and static pressure loss;

FIG. 6 is a view similar to FIG. 5, but with the plate fin turned 180 so that, similarly to the plate fin shown in FIG. 3, it is so arranged with respect to air flow as to provide low heat transfer and static pressure loss; and

FIG. 7 is a perspective view on an enlarged scale of a corner of the plate fin of FIGS. 5 and 6.

With reference now to the details of the above-described drawings, the tube bundle shown in part in FIG. 1, and designated in its entirety by reference character 10, includes a header 11 connected to opposite ends of longitudinally and laterally extending, spaced apart rows of tubes. In this instance, there are three longitudinally extending rows of tubes and thirteen laterally extending rows of tubes. There is an inlet 12 on the top side and an outlet 13 on the bottom side of each header 11 to permit the circulation of fluid into and through the tubes connected with the header.

A multiplicity of plate fins 14 are disposed about the tubes intermediate the headers at the opposite ends of the tubes. As well lmown in this art, these plate fins are closely spaced apart and, as to be described hereinafter, have interruptions in their surfaces to increase the heat transfer characteristics. In the illustrated environment of the tube bundle 10, air would be caused to flow past the tubes in a vertical direction, either from above or below.

As illustrated in FIGS. 2 and 3, the longitudinally extending rows of holes 15A in each plate fin 14A, constructed in accordance with the one embodiment of this invention, are arranged along spaced apart axes X. AS

will also be apparent from these figures, the laterally extending rows of these holes are arranged along spaced apart axes Y. The axes X, and thus the longitudinally extending rows of holes, are arranged perpendicularly to the axes Y, and thus the laterally extending rows of holes, so that, as previously described, the holes, and thus the tubes adapted to be received through them in the assembly of the tube bundle 10, are arranged in a rectangular pattern. Thus, with air flowing a direction perpendicular to either longitudinal edge of the plate fin, as indicated in FIGS. 2 and 3, the tubes of the bundle will be in line with it.

As can be seen from FIGS. 2 and 3, a louver 16A is disposed within each such rectangular area formed by adjacent longitudinally and laterally extending rows of holes and extends longitudinally or parallel to the axes X. More particularly, each louver 16A is arranged asymmetrically of a straight line Z extending parallel to and equidistant the axes of adjacent axes X. Thus, with the air flow upwardly, and the plate fin arranged as shown in FIG. 2, the louver 16A is nearer the throat between the upstream holes of each rectangular area. On the other hand, in the reversed position of the plate fin shown in FIG. 3, the louver is nearer the throat of the downstream pair of holes of each such rectangular area.

As previously mentioned, the arrangement of the plate fin 14A with respect to air flow shown in FIG. 2 results in higher heat transfer and static pressure loss. The higher heat transfer results from the fact that this arrangement causes more air to be diverted into the otherwise dead space on the downstream side of each hole. At the same time, however, there is greater air velocity at the time it impinges on the louver, so that there is consequently greater static pressure loss.

In the arrangement of the plate fin with respect to air flow shown in FIG. 3, less air is diverted into the above-mentioned otherwise dead air spaces, because the louver is closer to the downstream throat between the holes of the rectangular area than to the upstream throat. However, this arrangement results in less static pressure loss since there is less velocity of the air flow at the time it impinges on the louver.

As previously mentioned, this reversible characteristic of the plate fin enables the tube bundle to be used in instances in which the heat transfer rate of the tube side fluid is either high or low, and thus controlling or not controlling, as the case may be.

Still further, the plate fins may be stacked in edge-toedge relation to provide still other heat transfer and static pressure loss relationships. Thus, for example, the lower longitudinal edge of a plate fin arranged as shown in FIG. 3 may be disposed adjacent the upper longitudinal edge of a plate fin arranged as shown in FIG. 2. Then, with the flat faces of the plate substantially coplanar, the resulting composite fin, which would include six longitudinally extending rows of holes 15, would obviously result heat transfer and static pressure loss values different from those above-described. More particularly, this would be possible without the need for another die for punching louvers in an integral plate having the six longitudinally extending rows of holes.

In the illustrated and preferred embodiment of the invention, there is only one interruption in the form of a raised louver, which, as best illustrated in FIG. 4 is merely punched out from one side of the plate 14A. This construction is particularly well suited for those installations in which the plate fin is to be made of steel, rather than aluminum. Steel is preferred in many installations because of its resistance to high temperatures, where, on the other hand, aluminum loses its temper at 500 C. When the plate is of steel, only the single louver is used because of the low heat conductivity of the plate.

Preferably, each louver 16A is not only arranged asymmetrically of the straight line Z, but also is disposed on one side or the other of such straight line. In this way, the plate fin may be formed of any desired number of longitudinally extending rows, and then cut to desired widthsi.e., with less than the original number of longitudinally extending rows.

As illustrated, the louver is preferably arranged symmetrically with respect to a straight line (not shown) parallel to and equidistant the laterally extending axes Y. As also illustrated, the louver is not too close to the throat of either the upstream or downstream pair of holes of each rectangular area of the plate. Thus, as illustrated in FIGS. 2 and 3, the opposite ends of each louver terminate short of a tangent to the near sides of the holes of the rectangular area in which the louver is disposed. Similarly, the side of the louver opposite the straight line Z terminates short of a tangent to the near sides of the holes of each such area.

In the embodiment of the plate fin 14A, the distance between each longitudinal edge of the plate and the adjacent axis X is equal to one-half the distance between adjacent axes X. Thus, there is an additional louver 16A between adjacent axes Y and one such longitudinal edge and its adjacent axis X. More particularly, this additional louver is asymmetrical with respect to such longitudinal edge in the same direction and spacing as the other louvers are asymmetrical with respect to centerline Z. Thus, in FIG. 2, this additional louver is downstream of the last longitudinal row of holes; and, in FIG. 3, it is upstream of the first row thereof.

As also shown in each of FIGS. 2, 3 and 4, there is a series of short louvers 16A between each lateral end of the plate fin and the adjacent laterally extending row of holes. The length of these louvers will, of course, depend upon the spacing between the lateral edge and axis Y of the adjacent lateral row of holes, which, ordinarily, will be one-half the distance between the axes Y of the adjacent laterally extending rows. In any case, however, regardless of its length, the end of each short louver 16A is spaced from its adjacent hole 15A in the same manner as the end of the other louvers 16A.

As shown in FIG. 4, there are tabs 17A spaced about each hole 15A for receiving and firmly gripping a tube. Although this type of gripping means is satisfactory for use with plate fins made of steel, other types may be desirable in the case of aluminum plate fins. In any case, the means by which the fins are gripped by the plates forms no part of the present invention.

The plate fin 14B, which is constructed in accordance with the other embodiment of this invention shown in detail in FIGS. 5 and 7, also has longitudinally and laterally extending rows of holes 15B arranged along spaced apart axes X and Y, respectively, which are perpendicular to one another. Thus, as in the case of the plate fin 14A, the holes 15B and thus the tubes adapted to be received through them are arranged in a rectangular pattern, so that the tubes of the bundle will be in line with air flowing in a direction perpendicular to either lsongituginal edge of the plate fin, as shown in FIGS.

and

As is also the case in the plate fin 14A, a louver 16B is disposed within each rectangular area formed by adjacent longitudinally and laterally extending rows of holes 15B. More particularly, the louver 16B extends longitudinally or parallel to the axes X and is arranged asymmetrically of a straight line Z extending parallel to and equidistant the axes of adjacent axes X. Thus, with the air flow past the plate fin in an upward direction, as shown in FIG. 5, the louver 16B is nearer the throat between the upstream holes of each rectangular area. As

in the case of the plate fin 14A, a tube bundle with this arrangement of the plate fin 14B results in higher heat transfer and static pressure loss. 0n the other hand, in the reversed position of the plate fin 14B shown in FIG. 6, wherein the louver 16B is nearer the throat between the downstream holes of each rectangular area, there is less static pressure loss and heat transfer in the tube bundle.

As distinguished from the plate fin 14A, there are additional louvers 18B disposed within each rectangular area formed by adjacent longitudinally and laterally extending rows of holes in the plate fin 14B. More particularly, there are a pair of additional and identical louvers 18B which extend longitudinally and parallel to the axes X and which are spaced equidistant from and on opposite lines of the straight line Z so as to be symmetrical with respect thereto. This construction is particularly Well suited for those installations in which the plate fin is made of aluminum, and wherein additional turbulence is desired.

The asymmetrical louver 16B is disposed on the outer side of one of the symmetrical louvers 18B, so that with the symmetrical louvers 18B straddling such straight line, the plate fin 14B may also be formed of any desired number of longitudinally extending rows, and then cut to the desired widthsi.e., with less than the original number of longitudinally extending rows.

As illustrated, each of the asymmetrical louvers 16B and symmetrical louvers 18B is preferably arranged symmetrically with respect to a straight line (not shown) parallel to and equidistant the laterally extending axes Y. Since the symmetrical louvers 18B are arranged closer to the straight line Z then the asymmetrical louvers 16B, each such symmetrical louver may be longer than the asymmetrical louver.

As in the plate fin 14A, the distance between each longitudinal edge of the plate fin 14B and the adjacent axis X is equal to one-half the distance between adjacent axes X. Thus, there is an additional asymmetrical louver 16B between adjacent axes X and one such longitudinal edge. More particularly, this additional louver is asymmetrical with respect to such longitudinal edge in the same direction and spacing as the other louvers 16B are asymmetrical with respect to the centerline Z. Furthermore, there is one symmetrical louver 18B adjacent each longitudinal edge which, together with the asymmetrical louver, is downstream of the last longitudinal row of holes in FIG. 5, and upstream of the first row thereof in FIG. 6.

As also shown in FIGS. 5 to 7, there is a series of short asymmetrical louvers 16B between each lateral edge of the plate fin and the adjacent laterally extending row of holes. Additionally, there are pairs of short symmetrical louvers 188 between each lateral end of the plate fin and the adjacent laterally extending row of holes. The length of these short louvers depends, of course, upon the spacing between the lateral edge and the axis Y of the adjacent lateral row of holes. In any case, one end of each of the short asymmetrical and symmetrical louvers is spaced from the adjacent hole 15A in the same manner as the ends of the louvers 16B and 18B.

As shown in FIG, 7, there are collars 17B about each hole 153 in the plate fin 14B for receiving and gripping a tube. This type of gripping means is best suited for use with plate fins made of aluminum, as is contemplated in the case of the plate fin 14B.

From the foregoing, it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth, together with other advantages which are obvious and which are inherent to the apparatus.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimed 1. A plate fin tube module, comprising an assembly of laterally and longitudinally extending, spaced apart rows of parallel tubes, and a plurality of closely spaced, parallel plate fins having holes therein tightly engaged about the tubes, each plate fin being discrete with respect to the other plate fins, and the axes of said laterally extending rows of tubes being perpendicular to the axes of the longitudinally extending rows thereof so that the tubes of said module may be disposed in line with air flow past the longitudinally extending edges of the plate fins, each area of the plate intermediate the axes of adjacent laterally and longitudinally extending rows of tubes having at least one substantially longitudinally extending interruption arranged asymmetrically of a straight line extending parallel to and equidistant the axes of adjacent longitudinally extending rows thereof.

2. A module of the character defined in claim 1, wherein the surface of the area of each plate fin between adjacent tubes in each laterally extending row of tubes is smooth and free of interruptions.

3. A plate fin tube module, comprising an assembly of laterally and longitudinally extending, spaced apart rows of parallel tubes, and a plurality of closely spaced, parallel plate fins having holes therein tightly engaged about the tubes, each plate fin being discrete with respect to the other plate fins, and the axes of said laterally extending rows of tubes being perpendicular to the axes of the longitudinally extending rows thereof so that the tubes of said module may be disposed in line with air flow past the longitudinally extending edges of the plate fins, each area of the plate intermediate the axes of adja cent laterally and longitudinally extending rows of tubes having only one surface interruption, said one interruption extending substantially logitudinally of the fin and arranged asymmetrically of a straight line extending parallel to and equidistant the axes of adjacent longitudinally extending rows thereof.

4. A module of the character defined in claim 3, wherein the surface of the area of each plate fin between adjacent tubes in each laterally extending row of tubes is smooth and free of interruptions.

5. A module of the character defined in claim 3, wherein each said interruption is disposed between tangents to the inner sides of the tubes of said adjacent longitudinally extending rows of tubes.

6. A module of the character defined in claim 5, wherein the surface of the area of each plate fin between adjacent tubes in each laterally extending row of tubes is smooth and free of interruptions.

7. A plate fin tube module, comprising an assembly of laterally and longitudinally extending, spaced apart rows of parallel tubes, and a plurality of closely spaced, parallel plate fins having holes therein tightly engaged about the tubes, each plate fin being discrete with respect to the other plate fins, and the axes of said laterally extending rows of tubes being perpendicular to the axes of the longitudinally extending rows thereof so that the tubes of said module may be disposed in line with air fiow past the longitudinally extending edges of the plate fins, each area of the plate intermediate the axes of adjacent laterally and longitudinally extending rows of tubes having a pair of substantially longitudinally extending surface interruptions arranged symmetrically of a straight line extending parallel to and equidistant the axes of adjacent longitudinally extending rows thereof and another substantially longitudinally extending surface interruption at the side of one interruption of said pair and arranged asymmetrically of said straight line.

8. A module of the character defined in claim 7, wherein the surface of the area of each plate fin between adjacent tubes in each laterally extending row of tubes is smooth and free of interruptions.

9. A module of the character defined in claim 7, wherein each said asymmetrical interruption is disposed substantially within tangents to the inner sides of the tubes of said adjacent longitudinally extending rows of tubes.

10. A module of the character defined in claim 9, wherein the surface of the area of each plate fin between adjacent tubes inv such laterally extending row of tubes is smooth and free of interruptions.

References Cited UNITED STATES PATENTS 2,630,009 6/1954 Nekut 165 47 X 3,135,320 6/1964 Forgo 165181X 3,223,153 12/1965 Simpelaar 165--152 FOREIGN PATENTS 177,364 5/1935 Switzerland.

10 ROBERT A. OLEARY, Primary Examiner.

THEOPHIL W. STREULE, Assistant Examiner.

US. Cl. X.R. 29-1573; 113118 

